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KEF X300AAudiophiles are a conservative bunch. And audio reviewers are, it seems, even more so. The new is often regarded with skepticism, which is part of why many cling to the “musicality” of vinyl and the “warmth” of vacuum tubes. It’s familiar to the pasty old men who’ve been reviewing for years, and the longer they subscribe to a given perspective, the more difficult it becomes to dislodge. So it’s not surprising when something as wildly talented as it is unorthodox doesn’t earn the attention it’s due.

KEF’s X300A loudspeakers ($799.99/pair USD), released in the latter half of 2012, have been mostly reviewed by computer and consumer-electronics publications. Seeing as the speakers are powered and cost under $1000, perhaps the traditional hi-fi publications assumed that these slate-gray speakers are merely glorified computer speakers. Or perhaps they thought that no audiophile would be interested in using them in lieu of a more conventional stereo system. Whatever their reasoning, they’re buffoons for not having seen the deep significance of these loudspeakers.

Computer speaker-ish

Here is the premise of the X300A: a quality bookshelf speaker with built-in amplifiers and digital and analog inputs. Relatively straightforward stuff, and not something that is, at first blush, in danger of raising one’s heart rate. Let’s delve deeper.

Each X300A measures 11”H x 7.1”W x 9.6”D (the depth includes the heatsink on each cabinet’s rear) and weighs 16.5 pounds -- pretty substantial for a predominantly desktop model, they feel very solid. The entire cabinet is made of MDF wrapped in high-quality vinyl; the only seam is on the bottom panel, between the built-in footers.

The foundation of the X300A is its Uni-Q driver, from KEF’s Q100 bookshelf model ($549.99/pair). This coaxial driver comprises a vented 1” aluminum dome nestled in the center of a 5.25” midrange-woofer cone made of an alloy of aluminum and magnesium. Drawing on the design principles KEF used in their Blade speaker ($30,000/pair), the Uni-Q’s surround is ribbed to minimize diffraction problems. The tweeter also has what KEF calls its “tangerine” waveguide, a starburst-shaped piece of metal that sits atop the aluminum diaphragm to protect it from prodding fingers and aid in controlling its dispersion of treble frequencies. While coaxial or coincident drivers can often image better than more traditional driver arrays, having one driver radiating from within another presents the speaker designer with a variety of challenges. KEF is confident that, as with their LS50 minimonitor (an instant classic) and R900 floorstanders (my reference speakers), the latest generation of their coaxial drivers are something special.


The Uni-Q is mounted flush with the X300A’s front baffle, which is made of a 0.5”-thick polymer designed to minimize vibration. Its classy, brushed-slate appearance is something you’ll see often -- the X300As have no grilles. The only difference between the two speakers’ fronts is a tiny light above the driver of the left X300A. It glows red when the speakers aren’t receiving a signal, green when they are. Unlike many other audio components I’ve seen in the past few years, it’s a subtle indicator that won’t light up an otherwise darkened room.

A sizable heatsink and port occupy a fair amount of space on the rear of each speaker, along with an IEC power inlet -- yes, two X300As require two power outlets. The right speaker has a balance control; the left speaker has an On/Off switch, a system gain control, a mini-USB input for use with a computer, and a 3.5mm analog input. Both speakers have mini-USB ports for the signal umbilical that links them. Lastly, there’s an EQ switch for switching between Desk and Stand use. When Desk is selected, the bass level is reduced; in Stand mode, the bass level remains flat. KEF includes a pair of power cords, a pair of USB cables with full-size Type-A connections on one end and mini Type-B plugs on the other, and a 3.5mm analog stereo cable. Lastly, a pair of clever two-way plugs are included, each with a removable central section to permit full or partial blocking of the rear ports. As will be addressed below, these are vital to tailoring the X300As’ bass response to your setup.


Inside the X300A, things get interesting. Inside each speaker are two amplifiers: a 20W unit to power the tweeter, and a 50W amp to drive the midrange-woofer. These class-AB amps, designed by KEF specifically for the X300A, let the speaker attain a maximum peak output rating of 104dB, which should be plenty loud enough for nearfield desktop use. There are also two digital-to-analog converters -- one in each speaker. This permits a fully digital, asynchronous USB signal path between the Burr-Brown PCM 1754 chips. Interestingly, the 3.5mm analog input jack is routed through the DAC; when the X300A is connected to a cell phone or tablet, a digital music file sent from that source would be converted to analog out of the device, to digital on the way into the KEFs via the built-in Wolfson WM8782 analog-to-digital converter, then back to analog. While this may not be the neatest setup -- the analog inputs on Devialet’s line of integrated amplifier-DACs function in much the same way -- it means that every source will be able to take advantage of a pair of reasonably high-quality DACs.

Omissions? A remote control would have been nice, though I think it would go largely unused; most users will probably control the KEFs’ volume through a connected computer. Another digital connection, say of the optical variety, and/or another analog input might have also been convenient, but I think these, too, would be mostly ignored. As most X300As will probably be used on desktops, I can’t imagine plugging more than two sources into them. Last, I can imagine that a few buyers would crave access to a subwoofer output, which is also lacking. Given the bass performance on offer here (see below), I suspect there are few who would desire a sub’s extension of the low bass and have the additional space a sub would demand. The balance of simplicity and connectivity that KEF strikes here is a thoughtful one that is probably sufficient for 95% of its intended audience.


Let’s sum up: A pair of competent coaxial drivers borrowed from a $549.99/pair passive loudspeaker, and derived from KEF’s utterly original, $30,000 Blade project. A properly dense, well-built, cleanly appointed cabinet. Four class-AB amplifiers designed and manufactured by KEF specifically for this model. Two DACs. An asynchronous USB connection able to handle signals of up to 24-bit/96kHz resolution. And a 3.5mm connection able to harness the speakers’ own prowess at digital conversion. All of a sudden, $799.99 sounds like a pretty modest sum.

Some notes on setup

While I listened quite a bit to the X300As as they perched on 24”-high stands, as in a traditional hi-fi setup, how far apart they can be placed is limited by the length of the included USB digital-umbilical between them. USB cables are limited to about 5m in length, due to problems with signal integrity at greater lengths; odds are that in this setup, you’ll have an almost straight length of cable suspended between the two cabinets, as I did. Not the most elegant arrangement.

The KEFs were much more at home on a desk, though their size warrants spacing as wide as possible, with some distance from a front wall and, if plausible, with the drivers at or near ear level -- none of which I had the benefit of doing. Instead, they sandwiched the laptop computer and external monitor that I use when working from home during the week, and sat level on my desk with their rear panels right up against a wall -- hardly ideal, but my city apartment severely limits my options. The convenient thing, though, was that whether I used my computer via USB, my computer via stereo miniplug, or any other source, the X300As went into standby mode within a few minutes of not being fed a signal, or as soon as a source was physically disconnected. Connection via USB was easy. I simply selected the KEFs in Apple’s Audio MIDI utility, and my MacBook Pro automatically recognized the speakers from then on.


I was surprised by the sound of the KEF X300As, though not in a “this is a giant killer” kind of way. Yes, the sound was excellent for an entire amps-and-speakers system for well under $1000, but I don’t think the X300A was as much of an overachiever as its passive cousin, the LS50 ($1499.99/pair). What struck me was the X300A’s disarming tonal balance, and its top-to-bottom, thoroughly hi-fi presentation.

Unlike my reference speakers, KEF’s R900s ($4999.98/pair), which have a transparent, ultraclean sound, the baby X300As had a bit more personality. They sounded quite smooth, and their midrange had a slightly rich, golden quality that, while not quite neutral, came pretty close. Voices tended to bloom a little more through the X300As than through other competing designs I’ve heard, but this lent the sound an engagingly immersive quality.

“Angels,” from the xx’s Coexist (16-bit/44.1kHz AIFF, XL/Young Turks), is a rumination on young love supported by a spare arrangement. When I had the X300As mounted on stands, way the hell out from my front wall, lead singer Romy Croft’s voice hung with real weight -- none of that threadbare stuff that cheap class-D amps can put out -- and imaging was good, if not exactly exceptional. Whereas Paradigm’s terrific Millenia CT wireless sat-sub system ($699.99) was better, in its more finely delineated imaging and soundstage depth, than the KEFs, the Paradigms also had an überclean sound that wasn’t kind to poor recordings. In that sense, the KEFs were more forgiving and, in some ways, more alluring. The KEFs offered no less detail than the Paradigms -- the difference was in how that detail was portrayed.

201310 kefpair

The X300As’ highs, too, were excellent, their aluminum tweeters providing a fine treble companion to the hearty midrange. “Spitfire,” from The Prodigy’s Always Outnumbered, Never Outgunned (16/44.1 AIFF, XL), is a riot of a song -- a raucous powerhouse of distorted, screaming voices, and a punishing assortment of drums, cymbals, and guitar riffs. Whereas the Paradigms render all this with sparkling crispness through the highs, the KEFs were a little gentler in nature, and probably more neutral -- they didn’t stray too far in the other direction, to make the sound dark and closed-in. Though the X300As handled everything well, I think their tweeters were the highlight here.

Which leads me to the X300A’s bass. The extension was admirable for a speaker of this size, and KEF’s claimed frequency response of 58Hz-28kHz, ±3dB, sounds accurate, though I suspect there was a dose of midbass boost -- the X300As sounded a little bass-heavy, whether sitting on stands or on my desk, even when I chose the appropriate EQ setting (Stand or Desk), which affects the bass level. “Around the World / Harder, Better, Faster, Stronger” is a lovely mix by Daft Punk from their last live album, Alive 2007 (16/44.1 ALAC, Virgin). It has some deep synthesizers that the X300As couldn’t wholly reproduce, which was to be expected, but that seemed slightly overdone in the upper bass. The Paradigm Millenia CT, with its dedicated subwoofer’s 8” cone, offers bass that’s both deeper and more tuneful. But this, too, is to be expected -- the X300A has all the strengths and limitations of a strict two-box system, which is what it is. The two-way port plugs were useful in minimizing this emphasis in the lower registers, even if doing so ultimately detracted from the speakers’ full, weighty sound.

I did my best to torture the KEFs by playing them very loudly. The mids and highs seemed to scale without objection, but I could tell that the X300As were struggling to keep up in the bass. They never distorted, but the bass did become looser as the volume increased. Mind you, this was louder than I’d ever want to play them, but they did have limits. The excursion of the midrange-woofers when playing the Daft Punk and other bass-heavy tracks was impressive, however, and at reasonable listening levels, I was pleased with both the quality and quantity of the X300As’ bass.


I compared the KEFs to Paradigm’s Millenia CT system. Given that the 2.1-channel Millenia costs $100 less than the X300As, and provides more impressive bass, you might expect that I’d prefer the former. I didn’t -- at least, not necessarily. The Millenia CT marries its two excellent satellite speakers to a dedicated subwoofer. But it also has a small, separate signal box, and a remote control that, if lost, renders the volume nonadjustable -- which, during the listening period, led to multiple occasions of unintentionally blaring very loud music. The separate signal box also meant that I had wires everywhere for a supposedly wireless system, and a sub that I needed to toss somewhere. Still, the Millenia CT makes a ton of sense as a sound system for a TV, while the KEFs worked pretty well everywhere except with a TV. Moreover, the intimate voicing of the X300As meant that they excelled on my desktop, provided I gave them the space they needed in order to sing. Most impressive, however, was that the KEF X300A is a comprehensive stereo hi-fi system in two boxes, as opposed to the Millenia CT’s four.

Consolidated hi-fi

KEF’s X300As are almost uncomfortably compelling. Their modest price belies their impressive heft and solid if understated design. They offer hi-fi sound from top to bottom, with an engaging midrange and ripe bass response. Most notably, the inclusion of a DAC means that one is only a computer away from a proper high-end system. That a product designed from the ground up by one of the most reputable speaker companies on the planet costs so little is an achievement. It just works so well and with such ease. Call it a gourmet computer speaker, a desktop hi-fi, or whatever you like -- just understand that this is the small beginning of something significant: the future of high-end audio.

. . . Hans Wetzel

Associated Equipment

  • Speakers -- KEF R900, Paradigm Millenia CT, PSB Alpha PS1, Sonus Faber Olympica I, Vivid Audio Oval V1.5
  • Integrated amplifiers -- Arcam A19, Hegel Music Systems H300, NuForce DDA-100
  • Sources -- Apple MacBook Pro running Songbird and iTunes
  • Speaker cables -- Dynamique Audio Caparo, Nordost Frey 2
  • Interconnects -- Dynamique Audio Shadow, Nordost Frey 2
  • USB cables -- DH Labs Silversonic, Nordost Blue Heaven LS
  • Power cables -- Nordost Frey 2

KEF X300A Powered Loudspeakers
Price: $799.99 USD per pair.
Warranty: Five years parts and labor.

Eccleston Road, Tovil
Maidstone, Kent
England ME15 6QP
Phone: +44 (0)1622-672261
Fax: +44 (0)1622-750653

Website: www.kef.com 

North America:
KEF America / KEF Canada, Inc.
10 Timber Lane
Marlboro, NJ07746
Phone: (732) 683-2356

E-mail: sales@kefamerica.com